The invention relates to a wire guide for a medical instrument, which has a guide wire core and a sheath which surrounds the guide wire core at least in places, and which is suitable for use, for example, for a medical instrument which is compatible with magnetic resonance imaging, MRI or MR for short, or nuclear magnetic resonance (NMR), and/or examinations with an X-ray application.
In conventional guide wires of this type, the guide wire core, also referred to as the core, is typically used to provide a desired stiffness for the guide wire, while the sheath is typically used to protect the core and/or for application of markings, and is accordingly formed from a material which is more flexible and/or softer than the core. German patent document DE 100 20 739 A1 discloses the specific case of markings which are visible in X-ray radiation.
In this case, it is also known for the guide wire core to taper in a distal, application-end front end section in order for this distal end section to be more flexible than an adjacent shaft section. The tapered core section may likewise be surrounded by a softer sheath or may be designed specifically in some other manner, depending on the requirements. For example, German patent document DE 101 38 953 B4 describes a guide wire with a core which tapers in a distal end section and is surrounded by a helical spring sheath. The spring sheath is connected to the front end of the tapered core via a blunt front end dome.
The invention is based on the technical problem of providing a novel guide wire that can be manufactured with relatively little effort in order to achieve a desired flexibility in at least one end section and a desired stiffness in an adjacent shaft section and, when required, be MRI-compatible and/or compatible with X-ray radiation.
These and other advantages are achieved by a guide wire having a guide wire core and a sheath that surrounds the guide wire core at least in places, wherein the sheath is formed at least in one shaft section, which is adjacent to an end section, with a greater stiffness than the guide wire core.
On the one hand, this allows relatively simple production, for example, from an endless base material composed of two or more different materials for the core and the. On the other hand, this satisfies the precondition of manufacturing at least one end section with a desired flexibility, as required, and in a manner which is simple from the production engineering point of view, as is typically required for guide wires for medical instruments. The one end section preferably has a stiffness which is noticeably less than that of the shaft section. According to one advantageous embodiment, the guide wire can be formed by cutting off the guide wire, for example, from an endless base material with the core and sleeve and removing the sleeve (which, according to the invention, is stiffer than the core) in the relevant end section such that it governs only the greater stiffness of the guide wire in the adjacent shaft section.
The end section with the remaining core may be processed further in some desired manner, for example, by applying a sleeve composed of a different material and/or by fitting one or more further components, depending on the purpose of the guide wire. The flexibility and stiffness of this end section are then not governed, as in the adjacent shaft section, by the sheath which is stiffer than the core, but by the core and/or the component or components which is/are additionally fitted there.
According to one embodiment of the invention, the choice of the material for the core on the one hand and of the sheath on the other hand can be specified independently.
According to a further embodiment of the invention, a distal flexible end section of the guide wire is surrounded by a sleeve whose stiffness is less than that of the sheath in the adjacent shaft section and/or that of the core. This makes it possible to produce the distal end section to be less stiff than the shaft section and accordingly to be more flexible, and at the same time to provide the core with a sleeve which may be matched to the desired purpose. In a further embodiment, an abrupt or continuous transition is provided as required between the sleeve of the distal end section and the sheath of the adjacent shaft section.
In another embodiment of the invention, the guide wire core has one or more individual cores which are distributed over the cross section of the stiffer sheath in the shaft section and are composed of a monofil or multi-fiber material and/or a composite material with a hard-elastic inner core and surrounding fabric material. This allows the stiffness or bending characteristics of the guide wire to be influenced or set in the desired manner according to the purpose in the corresponding section which has the stiffer sheath. By way of example, the stiffness of the shaft section can therefore be varied over a wide range depending on the composition, position and distribution of the individual core or cores and depending on the ratio of the core cross-sectional area to the cross-sectional area of the stiffer sheath.
In yet a further embodiment of the invention, one or more electrical conductors are provided in the core and/or in the sleeve. This makes the guide wire suitable for applications in which electric currents are passed through the guide wire. In a further embodiment, different connection options for the electrical conductors can be provided at the proximal guide wire end.
An MRI and/or X-ray functional unit, which makes the guide wire compatible with MRI and/or X-ray applications, can be provided in the distal end section of the guide wire.
In a further embodiment according to the invention, a spiral structure, a mesh structure, an electrical capacitor structure, an electrical coil structure and/or a separate end dome are/is provided in the distal end section. Components such as these are suitable for specific applications, for example, for providing an MRI function or X-ray visualization for producing electrical and/or magnetic fields and/or for providing sensor elements for measuring pressure, voltage, temperature and other variables.
In a still further embodiment according to the invention, the distal end section of the guide wire is provided with a sleeve that contains a filling material comprising solid or hollow material bodies that are distributed regularly or randomly, or the distal sleeve is provided using a hollow foam material with cavities arranged distributed regularly or randomly. This type of distal sleeve offers the capability to dope the cavities and/or the filling material with a foreign substance in order to set desired magnetic characteristics for the distal end section. By way of example, this may be advantageous for MRI applications.
Finally, according to yet another embodiment according to the invention, a spiral spring surrounding the core, and/or a tubular piece surrounding the core and/or a wire piece running alongside the core are/is provided in the distal end section of the guide wire. Each of the foregoing can act as an element that influences the flexibility of the distal end section such that the flexibility can be set specifically, starting from that of the core, by means of one or more of these elements.
Advantageous embodiments of the invention will be described in the following text and are illustrated in the drawings, in which:
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.